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Chap. Two: Chemical Interactions
Atoms and the Periodic Table
STRUCTURE and Parts of ATOMS
118 “basic kinds” of matter
Elements
92 naturally occurring (26 created in LABS)
All listed on periodic table of elements
Building blocks of everything on Earth
Atoms
– smallest unit (pieces) of elements
– Atoms combine to form compounds
STRUCTURE OF AN ATOM
Protons
• in the nucleus
– center of the atom
• positively charged
• mass of “1” (AMU)
EQUALS ATOMIC NUMBER
ATOMIC STRUCTURE…(cont’d)
Neutrons
– have no electrical charge
– mass of “1” (AMU)
• AMU = “atomic mass unit”
– in the nucleus
– number may vary
ATOMIC STRUCTURE (cont’d)
Electrons
– negatively charged
– mass of “0”
– in energy shells, or “orbits”
surrounding the nucleus
ELECTRON DISTRIBUTION
Electrons are organized in “clouds” or energy levels.
4 shells
•
•
•
•
2 in the first
8 in the second
8 in the third
2 in the last
Generally 8 is the most stable configuration.
Electrons and Chemical Bonding
“Sharing is caring…unless you’re ionic and
then you just steal.”
What do electrons do?
Attractions between electrons in their shells
causes chemical bonds to form.
Chemical bonds occur so that each atom in the
molecule has 8 in its outermost shell.
There are TWO types of chemical bonds:
Ionic and Covalent
ELECTRON DISTRIBUTION…cont’d
All atoms “want” 8 electrons in
their outermost shells and will
interact with other atoms to the
end that all reach 8.
TYPES OF CHEMICAL BONDS
IONIC - one atom loses electrons,
other gains electrons.
– atoms that lose electrons become more positively
charged
– atoms that gain electrons become more negatively
charged
This process forms IONS!!
TYPES OF CHEMICAL BONDS…cont’d
COVALENT
two atoms share one
or more pairs of electrons.
Each has 8 electrons in its outermost orbit.